The present invention relates to the cleansing of residue from sample transfer probes within analytical instruments so that the measurement error otherwise caused by cross-contamination between individual samples is avoided. Such cleansing is commonly accomplished in prior art instruments by flushing the probe both interiorly and exteriorly with a suitable non-contaminating liquid. Because of this flushing procedure, prior art instruments must include pumps, valves and containers for the flushing liquid which add to the design complexity and expense of such instruments.